This application claims the benefit of a Japanese Patent Applications No. 2000-126469 filed Apr. 26, 2000 and No. 2000-155722 filed May 26, 2000, in the Japanese Patent Office, the disclosure of which is hereby incorporated by reference.
1. Field of the Invention
The present invention generally relates to head speed control methods, head position detection methods and disk units, and more particularly to a head speed control method and a head position detection method which are suited for a disk unit having a ramp load and/or unload mechanism, and to a disk unit which employs such a head speed control method or a head position detection method.
2. Description of the Related Art
In a magnetic disk unit, a head writes and reads signals with respect to a magnetic disk. In the case of a hard disk, a small gap exists between the head and the disk. However, when the magnetic disk unit is mounted in a portable equipment such as a lap-top personal computer, the head is receded to a parking area other than on a recording surface of the disk when the magnetic disk unit does not carry out an operation, so as to prevent unwanted contact between the head and the disk due to an externally applied shock or the like. Otherwise, if the head hits the disk, there is a possibility of damaging the head and the disk.
In addition, when the magnetic disk unit is not used for a long period of time, the head may stick to the recording surface of the disk due to a lubricant or the like which is coated on the surface of the disk. For this reason, the head is receded to the parking area also when the magnetic disk unit is not used for a long period of time.
A ramp load/unload mechanism is provided to guide, along a ramp member, an arm which supports the head, during a ramp load operation in which the head is receded to the parking area and during a ramp unload operation in which the head is returned from the parking area onto the disk. During the ramp unload operation, the head separates from the disk, and thus, it is impossible to detect the position of the head or to detect and control the head speed, based on position information read from the disk. In addition, although the head speed during the time when the arm is guided by the ramp member can be predicted to a certain extent, it is impossible to accurately predict the head speed due to frictional wear of the ramp member and the like, changes introduced to constituent elements of the magnetic disk unit with time, and the inconsistencies of the characteristics among the individual magnetic disk units. It is possible to detect the head speed using a back electromotive voltage of a voice coil motor (VCM) which drives the head. But usually, the magnetic disk unit is constructed so that a base portion of the arm makes contact with a stopper and is stopped thereby when the head reaches the parking area during the ramp load operation in which the head is receded to the parking area.
Recently, in the portable equipment such as the lap-top personal computer which is mounted with the magnetic disk unit, the portable equipment is frequently operated using a battery as the power source, and there is a demand to minimize the power consumption. Consequently, power save modes are provided in the portable equipment so as to reduce the power consumption in steps depending on the state of the portable equipment, and the ramp load operation is carried out in some power save modes. There is a tendency for the frequency of carrying out the ramp load operation to increase, since there is a demand to further reduce the power consumption.
According to the conventional disk unit, there was a problem in that, even when the head speed is detected, it is impossible to detect the head position and to appropriately control the head speed during an operation such as the ramp load operation in which the head separates from the recording surface of the disk.
In addition, the conventional disk unit is constructed so that the base portion of the arm makes contact with and is stopped by the stopper every time the ramp load operation is carried out. Hence, a large mechanical contact noise is generated when the base portion of the arm hits the stopper. Consequently, there was a problem in that the contact noise is unpleasant to the user as the frequency of the ramp load operation increases.
Accordingly, it is a general object of the present invention to provide a novel and useful head speed control method, head position detection method and disk unit, in which the problems described above are eliminated.
Another and more specific object of the present invention is to provide a head speed control method which can appropriately control the head speed and a head position detection method which can detect the head position, even when the head is located at a position where the information on the disk cannot be read, and to provide a disk unit which can reduce the mechanical contact noise during the ramp load operation by employing such a head speed control method and/or head position detection method.
Still another object of the present invention is to provide a head speed control method for a disk unit having a head provided on a tip end of an arm, characterized by a step of switching and controlling a head speed to a plurality of target speeds which are set in advance, during at least one of a ramp unload operation in which the head is receded to a parking area other than on a recording surface of a disk and a ramp load operation in which the head receded at the parking area is returned on the recording surface of the disk.
A further object of the present invention is to provide a head position detection method for a disk unit having a head provided on a tip end of an arm, characterized by a step of detecting a head speed; and a step of detecting a time integration value of the head speed from a reference position from which a head position can be specified.
Another object of the present invention is to provide a disk unit provided with a motor which drives an arm having a head on a tip end thereof, characterized in that there are provided a first detection circuit detecting a head speed; and a second detection circuit detecting a time integration value of the head speed from a reference position from which a head position can be specified.
In the disk unit described above, the reference position may be a position where the head cannot read information on a disk.
In addition, the disk unit described above may further be provided with a controller which controls a ramp unload operation in which the head is receded to a parking area other than on a recording surface of a disk and a ramp load operation in which the head receded at the parking area is returned on the recording surface of the disk, and wherein the controller variably controls the head speed by controlling the motor during at least one of the ramp unload operation and the ramp load operation.
Furthermore, in the disk unit described above, the controller may control the motor to urge the head in a direction towards a terminal position of the parking area for a predetermined time when the head reaches the terminal position during the ramp unload operation.
Still another object of the present invention is to provide a disk unit provided with a motor which drives an arm having a head on a tip end thereof, characterized in that there is provided a controller switching and controlling a head speed to a plurality of target speeds which are set in advance, during at least one of a ramp unload operation in which the head is receded to a parking area other than on a recording surface of a disk and a ramp load operation in which the head receded at the parking area is returned on the recording surface of the disk.
In the disk unit described above, the controller may control the head speed to a predetermined target speed when the head reaches a predetermined position.
Further, in the disk unit described above, the controller may control the head speed to a predetermined target speed when a predetermined time is reached.
Therefore, according to the first aspect of the present invention, it is possible to realize a head speed control method which can appropriately control the head speed and a head position detection method which can detect the head position, even when the head is located at a position where the information on the disk cannot be read, and to realize a disk unit which can reduce the mechanical contact noise during the ramp load operation by employing such a head speed control method and/or head position detection method.
Another object of the present invention is to provide a disk unit provided with a ramp load mechanism, characterized by a load speed controller controlling a speed of a head when the head moves on a ramp member, and a circuit control processor controlling an operation of a peripheral circuit part while the speed of the head is controlled.
Still another object of the present invention is to provide a disk unit provided with a ramp load mechanism, characterized by a load speed controller controlling a speed of a head when the head moves on a ramp member, and a noise suppressing section suppressing a mixture of noise caused by an operation of a peripheral circuit part while the speed of the head is controlled.
A further object of the present invention is to provide a method of controlling a disk unit which is provided with a ramp load mechanism, characterized by the steps of controlling a speed of a head when the head moves on a ramp member, and controlling an operation of a peripheral circuit part while the speed of the head is controlled.
Still another object of the present invention is to provide a method of controlling a disk unit provided with a ramp load mechanism, characterized by the steps of controlling a speed of a head when the head moves on a ramp member, and suppressing a mixture of noise caused by an operation of a peripheral circuit part while the speed of the head is controlled.
Therefore, according to the second aspect of the present invention, in a disk unit which is provided with a ramp load mechanism, the operation of a peripheral circuit part is stopped or the operation is slowed down by reducing a clock frequency while a head speed signal is detected from a back electromotive voltage of a VCM when loading a head from a ramp member onto a magnetic disk, so as to suppress a noise which mixes into the head speed signal from the peripheral circuit part. As a result, it is possible to accurately and stably carry out the speed control during a ramp load operation based on the head speed signal which is detected from the weak back electromotive voltage of the VCM. In addition, it is possible to improve the reliability of the disk unit by preventing an erroneous operation which would otherwise be caused by an abnormal movement of the head when the ramp load operation is carried out.
Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.